This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is not a composition. Its East Asian Width is wide. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+1F3F4 offers a line break opportunity at its position, except in some numeric contexts.
The CLDR project calls this character “black flag” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: black, flag, waving.
This character is designated as an emoji. It will be rendered as colorful emoji on conforming platforms. To reduce it to a monochrome character, you can combine it with Variation Selector-15: 🏴︎ See the Emojipedia for more details on this character’s emoji properties.
The Wikipedia has the following information about this codepoint:
This is a list of flags which are entirely or largely black.
Representations
System
Representation (click value to copy)
Nº
127988
UTF-8
F0 9F 8F B4
UTF-16
D8 3C DF F4
UTF-32
00 01 F3 F4
URL-Quoted
%F0%9F%8F%B4
HTML hex reference
🏴
Wrong windows-1252 Mojibake
ðŸ´
Encoding: GB18030 (hex bytes)
94 39 C8 32
RFC 5137
\u'1F3F4'
Bash and Zsh inside echo -e
\U0001F3F4
C and C++
\U0001F3F4
C#
\U0001F3F4
CSS
\01F3F4
Excel
=UNICHAR(127988)
Go
\U0001F3F4
JavaScript
\uD83C\uDFF4
Modern JavaScript since ES6
\u{1f3f4}
JSON
\uD83C\uDFF4
Java
\uD83C\uDFF4
Lua
\u{1F3F4}
Matlab
char(127988)
Perl
"\x{1F3F4}"
PHP
\u{1f3f4}
PostgreSQL
U&'\+01F3F4'
PowerShell
`u{1F3F4}
Python
\U0001F3F4
Ruby
\u{1f3f4}
Rust
\u{1f3f4}
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